# git rev-parse -q --verify 56376c5864f8ff4ba7c78a80ae857eee3b1d23d8^{commit}
56376c5864f8ff4ba7c78a80ae857eee3b1d23d8
already have revision, skipping fetch
# git checkout -q -f -B kisskb 56376c5864f8ff4ba7c78a80ae857eee3b1d23d8
# git clean -qxdf
# < git log -1
# commit 56376c5864f8ff4ba7c78a80ae857eee3b1d23d8
# Author: Michael Ellerman <mpe@ellerman.id.au>
# Date:   Thu Apr 19 16:22:20 2018 +1000
# 
#     powerpc/kvm: Fix lockups when running KVM guests on Power8
#     
#     When running KVM guests on Power8 we can see a lockup where one CPU
#     stops responding. This often leads to a message such as:
#     
#       watchdog: CPU 136 detected hard LOCKUP on other CPUs 72
#       Task dump for CPU 72:
#       qemu-system-ppc R  running task    10560 20917  20908 0x00040004
#     
#     And then backtraces on other CPUs, such as:
#     
#       Task dump for CPU 48:
#       ksmd            R  running task    10032  1519      2 0x00000804
#       Call Trace:
#         ...
#         --- interrupt: 901 at smp_call_function_many+0x3c8/0x460
#             LR = smp_call_function_many+0x37c/0x460
#         pmdp_invalidate+0x100/0x1b0
#         __split_huge_pmd+0x52c/0xdb0
#         try_to_unmap_one+0x764/0x8b0
#         rmap_walk_anon+0x15c/0x370
#         try_to_unmap+0xb4/0x170
#         split_huge_page_to_list+0x148/0xa30
#         try_to_merge_one_page+0xc8/0x990
#         try_to_merge_with_ksm_page+0x74/0xf0
#         ksm_scan_thread+0x10ec/0x1ac0
#         kthread+0x160/0x1a0
#         ret_from_kernel_thread+0x5c/0x78
#     
#     This is caused by commit 8c1c7fb0b5ec ("powerpc/64s/idle: avoid sync
#     for KVM state when waking from idle"), which added a check in
#     pnv_powersave_wakeup() to see if the kvm_hstate.hwthread_state is
#     already set to KVM_HWTHREAD_IN_KERNEL, and if so to skip the store and
#     test of kvm_hstate.hwthread_req.
#     
#     The problem is that the primary does not set KVM_HWTHREAD_IN_KVM when
#     entering the guest, so it can then come out to cede with
#     KVM_HWTHREAD_IN_KERNEL set. It can then go idle in kvm_do_nap after
#     setting hwthread_req to 1, but because hwthread_state is still
#     KVM_HWTHREAD_IN_KERNEL we will skip the test of hwthread_req when we
#     wake up from idle and won't go to kvm_start_guest. From there the
#     thread will return somewhere garbage and crash.
#     
#     Fix it by skipping the store of hwthread_state, but not the test of
#     hwthread_req, when coming out of idle. It's OK to skip the sync in
#     that case because hwthread_req will have been set on the same thread,
#     so there is no synchronisation required.
#     
#     Fixes: 8c1c7fb0b5ec ("powerpc/64s/idle: avoid sync for KVM state when waking from idle")
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/m68k-linux/bin/m68k-linux-gcc --version
# < git log --format=%s --max-count=1 56376c5864f8ff4ba7c78a80ae857eee3b1d23d8
# < make -s -j 40 ARCH=m68k O=/kisskb/build/powerpc-fixes_m68k-defconfig_m68k CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/m68k-linux/bin/m68k-linux-  defconfig
arch/m68k/configs/multi_defconfig:108:warning: symbol value 'm' invalid for NF_TABLES_INET
arch/m68k/configs/multi_defconfig:109:warning: symbol value 'm' invalid for NF_TABLES_NETDEV
arch/m68k/configs/multi_defconfig:214:warning: symbol value 'm' invalid for NF_TABLES_ARP
arch/m68k/configs/multi_defconfig:269:warning: symbol value 'm' invalid for NF_TABLES_BRIDGE
# make -s -j 40 ARCH=m68k O=/kisskb/build/powerpc-fixes_m68k-defconfig_m68k CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/m68k-linux/bin/m68k-linux-  
<stdin>:1239:2: warning: #warning syscall seccomp not implemented [-Wcpp]
<stdin>:1317:2: warning: #warning syscall pkey_mprotect not implemented [-Wcpp]
<stdin>:1320:2: warning: #warning syscall pkey_alloc not implemented [-Wcpp]
<stdin>:1323:2: warning: #warning syscall pkey_free not implemented [-Wcpp]
/kisskb/src/arch/m68k/mvme16x/config.c: In function 'mvme16x_hwclk':
/kisskb/src/arch/m68k/mvme16x/config.c:399:2: warning: #warning check me! [-Wcpp]
/kisskb/src/arch/m68k/mvme147/config.c: In function 'mvme147_hwclk':
/kisskb/src/arch/m68k/mvme147/config.c:152:2: warning: #warning check me! [-Wcpp]
/kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl':
/kisskb/src/kernel/printk/printk.c:183:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/ipc/shm.c: In function 'ksys_shmdt':
/kisskb/src/ipc/shm.c:1637:59: warning: 'file' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/acct.c: In function 'acct_pin_kill':
/kisskb/src/kernel/acct.c:177:2: warning: value computed is not used [-Wunused-value]
/kisskb/src/lib/mpi/mpicoder.c: In function 'mpi_read_raw_from_sgl':
/kisskb/src/lib/mpi/mpicoder.c:336:12: warning: 'buff' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/core/gen_stats.c: In function '__gnet_stats_copy_basic':
/kisskb/src/net/core/gen_stats.c:149:19: warning: 'seq' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/core/flow_dissector.c: In function '__skb_flow_dissect':
/kisskb/src/net/core/flow_dissector.c:789:7: warning: 'vlan' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/core/dev.c: In function 'validate_xmit_skb_list':
/kisskb/src/net/core/dev.c:3176:15: warning: 'tail' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/proc/inode.c: In function 'proc_reg_open':
/kisskb/src/include/linux/list.h:65:12: warning: 'pdeo' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/proc/inode.c:340:21: note: 'pdeo' was declared here
/kisskb/src/lib/rhashtable.c: In function 'rht_deferred_worker':
/kisskb/src/lib/rhashtable.c:269:2: warning: 'next' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/lib/rhashtable.c:234:28: note: 'next' was declared here
/kisskb/src/fs/ocfs2/file.c: In function 'ocfs2_file_write_iter':
/kisskb/src/fs/ocfs2/file.c:2386:3: warning: value computed is not used [-Wunused-value]
/kisskb/src/fs/udf/unicode.c: In function 'udf_name_conv_char':
/kisskb/src/fs/udf/unicode.c:157:15: warning: 'c' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/net/macsec.c: In function 'macsec_del_rxsa':
/kisskb/src/drivers/net/macsec.c:1926:2: warning: 'assoc_num' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/net/macsec.c:1926:2: warning: 'rx_sc' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/net/macsec.c: In function 'macsec_del_txsa':
/kisskb/src/drivers/net/macsec.c:2003:2: warning: 'assoc_num' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/net/macsec.c:2003:2: warning: 'tx_sc' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/net/macsec.c: In function 'macsec_upd_txsa':
/kisskb/src/drivers/net/macsec.c:2068:5: warning: 'assoc_num' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/net/macsec.c:2068:24: warning: 'tx_sc' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/net/macsec.c:2069:21: warning: 'secy' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/net/tun.c: In function 'tun_get_user':
/kisskb/src/drivers/net/tun.c:1827:30: warning: 'copylen' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/net/tun.c:1537:31: warning: 'linear' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/drivers/net/tun.c:1737:46: note: 'linear' was declared here
/kisskb/src/fs/posix_acl.c: In function 'get_acl':
/kisskb/src/fs/posix_acl.c:147:3: warning: value computed is not used [-Wunused-value]
Completed OK
# rm -rf /kisskb/build/powerpc-fixes_m68k-defconfig_m68k
# Build took: 0:00:28.973345